Add licenseIdMigrationMessages. Resolves #5109.

[phadej]

Please include the following checklist in your PR:

• Patches conform to the coding conventions.
• Any changes that could be relevant to users have been recorded in the changelog.
• The documentation has been updated, if necessary.
• If the change is docs-only, [ci skip] is used to avoid triggering the build bots.

Please also shortly describe how you tested your change. Bonus points for added tests!

[gbaz]

Add the indefinite article: "Consider using a proper license." :-)

[hvr]

That's good idea!

[phadej]

For the record, PublicDomain is hard, but my IANAL-understanding:

copyright: Public Domain
license: CC0

is what you'd write. (In my jurisdiction even I write so, I'll still retain copyright!)

https://en.wikipedia.org/wiki/Comparison_of_free_and_open-source_software_licenses#Approvals

• CC0 isn't approved or rejected by OSI, Recommended by FSF (If you want to release your work to the public domain, we recommend you use CC0.: https://www.gnu.org/licenses/license-list.en.html#CC0)
• Unlicense has partial approval by OSI: while considered free not recommended
• Both are FSF approved and compatible with GPL-3.0

[phadej]

I'm not sure what happens on travis

/home/travis/build/haskell/cabal/dist-newstyle/src/pretty-show-1.6.16/dist: renamePath:rename: unsatisfied constraints (Directory not empty)Configuring library for pretty-show-1.6.16.

[angerman]

@phadej I keep seeing that as well. Initially I thought I'd blame the basedir patch (#4874), but as that hasn't been merged yet. I'm also a bit confused.

What apparently happens is that there Pretty.Text.Parser module (generated by alex/happy I believe) ends up in pretty-show/dist/build, and for some reason, cabal tries to rename the dist part (it's in cabal-installs Install.hs I believe). Not sure why we try to rename it. But that somehow trips up in System.Directory and ends up throwing a Directory not Empty exception.

However, while I occationally can reproduce this locally, when I try to run it verbosely (-v), it doesn't happen.

[angerman]

PS: restarting travis jobs might help (and will eventually turn green...)